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Author Topic: CW Touch-Tone Syndrome  (Read 5165 times)
AJ8MH
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« on: March 05, 2013, 11:26:12 AM »

This is NOT meant to start a debate on the legal use of MCW.  It's just a reminder that one needs to be aware of what your MCW signal sounds like if your gear isn't adjusted properly.

I'm hearing more and more dual-tone CW signals in the pileups these days, and I can only assume it's from soundcard generated MCW.  I'm also hearing (and seeing) wideband noise, and occasionally hearing conversations through microphones that aren't muted.  Please, double-check your equipment.

Small circuits that convert soundcard audio to a switched ground for keying are easy to build.

73,
Joe



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PA0BLAH
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« Reply #1 on: March 05, 2013, 12:15:07 PM »

When you switch a carrier on and off, that is true CW. May be it has clicks due to bad shaping of the envelope of the signal.

When you buy a SSB transceiver, and the CW mode A1A (which is an add-on for the would be) is generated by a tone in the
audio channel, you get you mentioned MCW. Due to the fact it is SSB, you have one single signal with the tone offset of the suppressed carrier, however the  other sideband is not suppressed infinite, so there is a second signal at least 40 dB lower level than your primary desired product in the ether. When you put an oscilloscope on your antenna , may be you see small amplitude modulation with the double frequency of your tone, That is the interference with the undesired product. 40 dB down is 1 %, just visible.

The guys with a keyboard and SDR generate SSB and MCW with higher sideband suppression, die to the digital reproducible, temperature independent processing.

When you have a waterfall display, it may be interesting to show the phenomena you report here.
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AJ8MH
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« Reply #2 on: March 15, 2013, 05:01:49 PM »

I just heard another one of these, but this one was real bad.  He was also transmitting background noise.  I sent him an email just to let him know.  These touch-tone signals really stand out in a pileup.
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AB9NZ
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« Reply #3 on: March 16, 2013, 06:31:54 PM »

AJ8MH said:
Quote
These touch-tone signals really stand out in a pileup.
Hmmm, I think I need one of these touch tone transmitters Wink
   Best of 73 de Tom, ab9nz
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AJ8MH
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« Reply #4 on: May 16, 2013, 12:20:24 PM »

Heard another interesting CW signal yesterday.  Each time the station finished a dit or dah I could hear a "boink" about two khz up in freq. Boink! Boink! Boink! Boink! Boink!  Bands are getting interesting on CW.  Backwave?
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N3QE
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« Reply #5 on: May 17, 2013, 06:54:32 AM »

I think at least some of those phone-on-CW-bands things you are hearing, are phone QSO's in central or south america, where evening usage especially on 40M and 80M bands is quite common in their winter (our summer). Some of them are nets.

There are also some third-world southern hemisphere, non-ham, fishing boat phone patches set up in our CW bands.
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